Electrophoretic deposition is a process by which particles desired to be plated or deposited onto a substrate are first colloidally suspended and then urged out of suspension and onto a substrate by means of an applied electric field. The desired coating material is provided as an amount of colloidal particles suspended in a liquid (typically aqueous) medium. The particles are imparted a surface charge, and thus migrate under the influence of an applied electric field to be deposited onto a charged substrate, which acts as an electrode. The colloidal particles can be polymeric, metallic or ceramic, so long as they can hold a surface charge.
Electrophoretic deposition may be used for applying charged colloidal materials to any substrate that is, or that can be made, electrically conductive. Aqueous colloidal suspensions are typical of electrophoretic deposition. Non-aqueous electrophoretic deposition applications are being explored, but are still in their infancy and are primarily attractive for applications requiring voltages high enough to electrolyze water, which may result in the evolution of undesired amounts of oxygen.
Electrophoretic deposition is typically used to apply coatings to metallic items, such as machine parts, metallic structural members, containers, and the like. Current manufacturing methods for deposition of thin films onto substrates, such as silicon films for photovoltaic applications, typically utilize a vacuum environment in order to lower the crystallization temperatures of the amorphous silicon material used as a silicon source and deposited onto the substrate for subsequent heating and recrystallization. However, the electrophoretic deposition process is more difficult to control as the size of the suspended particles decreases. As coatings made up of smaller, nanoscale particles having interesting and useful properties are desired, there thus arises a need to an improved electrophoretic deposition process for providing such coatings. The present novel technology addresses this need.